Filtering of liquids, such as waste water, can for example be conducted with rotary disc filters comprising one or more filter discs. Filtering may take place both from the inside out and from the outside in depending on the filter disc. When filtering is to take place from the inside out, the rotor shaft has a hollow core and the liquid to be filtered is fed to the inside of the rotor shaft. The filter element and the rotor shaft have openings through which the liquid to be filtered is fed to the inside of a filter element. The filtering takes place from the inside of the filter element and out though a filter cloth arranged on the filter element. Particles in the liquid are separated from the liquid and remain on the inside of the filter cloth.
The filter disc typically comprises one or a plurality of filter elements attached to a rotor shaft creating the disc. The rotor shaft is usually capable of carrying a plurality of such disc filters and is for example a hollow drum that can host liquid. During operation, the rotor shaft carrying the filter discs is rotated and the filter discs are partially immersed in filtered liquid during rotation.
The filter elements according to the present invention can also be used in filter discs for filtering from the outside of the filter discs and into the rotor shaft, wherein particles are deposited on the outside of the filter cloth and the filtered liquid flows into the rotor shaft.